When you install Linux on a desktop PC, you normally choose from among a few “standard” graphics support components. You'll likely use the X Window system (XFree86 or ) as the display interface foundation (with associated Linux drivers to control the hardware), target=”_blank”>GNOME or KDE as a windowing environment, and one of several full-featured browsers such as Firefox, Konqueror, or Opera.

But the typical desktop Linux “graphics stack” isn't well suited to embedded Linux applications. Embedded devices frequently have highly constrained resources and can afford neither the program storage space nor the memory footprint of desktop graphics software. For example, embedded devices may easily have as little as 2 to 16 MB of Flash disk from which to load programs, and 4 to 32 MB of RAM memory in which to run them. But the typical desktop graphics components are notorious resource hogs . . .

X Window System: 5MB RAM, 16MB disk

GNOME: 14MB RAM, 95MB disk

KDE: 11MB RAM, 96MB disk

Mozilla: 12MB RAM, 26MB disk

All that memory costs money, requires board space, and consumes power. Then too, embedded systems frequently have unique needs that can't be met by desktop graphics system components. These include the requirement for a customized look and feel, control over what functions are available to users, speed of loading, unusual display or input device characteristics, etc.

To satisfy the demands of the rapidly emerging embedded Linux marketplace, a growing number of graphics support projects and products have sprung up. Targeted environments run the full gamut — including fixed, portable, and mobile systems — and the applications range from hand-held consumer products like PDAs and cell phones, to medical instruments, factory automation, and commercial airlines cockpit displays.

With this in mind, LinuxDevices.com has created The Embedded Linux Graphics Quick Reference Guide. We intend to continually update this guide — so be sure to check back frequently for the latest info.

Open source Embedded Linux Graphics System Software

Dillo — Dillo is a very small (less than 300KB), fast, Open Source multi-platform web browser that's written completely in C and built on GTK+ libraries. Dillo's high efficiency and minimal library dependencies make it quite suitable for embedded apps. Dillo can be teamed up with an embedded webserver to completely eliminate the need for a window manager in an embedded device. — details

DirectFB — DirectFB is a thin library that provides developers with hardware graphics acceleration, input device handling and abstraction, integrated windowing system with support for translucent windows and multiple display layers on top of the Linux Framebuffer Device. It is a complete hardware abstraction layer with software fallbacks for every graphics operation that is not supported by the underlying hardware. — details

The Familiar Project — this open source PDA Linux project, which is an offshoot of the activities at handhelds.org, has collected together all of the key components of a complete Linux-based PDA computing platform. The Familiar distribution currently includes a Blackbox-based window manager, Agenda Computing's Fltk+ based PIM applications, an embedded Python implementation, system configuration and settings backup utilities, OpenSSH client and server, and a Debian-based ARM kernel. — details

FBUI — FBUI is a tiny GUI that resides inside the Linux kernel. The key concepts of FBUI are that firstly it is small; secondly that it is spartan, which is good; thirdly that it is just another driver; and fourthly that drivers belong in the kernel, not in userspace. details

GGI project — the “General Graphics Interface” project is dedicated to development of fast, stable, open-source cross-platform multimedia API systems. Designed from the ground up with environments such as embedded systems in mind, GGI is fast, clean, abstract, dynamically modular and highly optimizeable. — details

GtkFB — beginning with version 2.0, GTK+ will support rendering directly to the Linux framebuffer instead of using the X Window System. This is good for embedded systems and devices with limited resources, because it eliminates the overhead of an X server, while still taking advantage of the power of GTK+ and the large base of existing programs. — details

handhelds.org PDA support — want to create your own unique Linux PDA implementation? handhelds.org is for you! Early this year, Compaq created the Open Handheld Program, an initiative designed to stimulate innovation and research on handheld devices that resulted from the company's “Itsy” pocket computer project. To support this initiative, Compaq created handhelds.org — a vendor neutral website dedicated to open source handheld development. Not surprisingly, Compaq's iPAQ PDA is used as the base platform for all these activities and, consequently, a iPAQ Linux port is available as freely available open source software. — details

Matchbox — a small foot-print window manager and associated applications, designed specifically for resource-constrained X11-enabled devices such as handheld computers, PDA's, set-top boxes, and consumer devices where display size, storage, CPU bandwidth, and input mechanisms are limited. Matchbox includes a window manager, a panel, a desktop, a shared utility library, and a number of small panel applications. — details

Microwindows — an Open Source project aimed at bringing the features of modern graphical windowing environments to smaller devices and platforms. Microwindows applications can be built and tested on the Linux desktop, as well as cross-compiled for the target device. — details

NxZilla (formerly nanozilla) — a set of libraries that allow Mozilla to be used with a NanoX server from the Microwindows project. — details

PicoGUI — small, portable client/server GUI designed to work on many types of hardware including handheld computers. Like the X Window System, it has a flexible client-server architecture. Unlike X, however, fonts, bitmaps, widgets, and anything else the application needs are built directly into the server. This sacrifices a small decrease in flexibility for an increase in speed and a large decrease in size. — details

Qt/Embedded — provides a full graphics stack, from the hardware interface to a full GUI tookkit. Although the API is identical to the popular Qt/X11 and Qt/Windows products, Qt/Embedded is not based on X11 and therefore it has substantially reduced memory requirements. Memory demands can be tuned to the range of 800 KB to 3 MB in ROM (Intel x86). Qt/Embedded is available as open source software, under the GNU General Public License (GPL), or can be licensed on other terms from its originator, Trolltech. — details

Simple DirectMedia Layer — an open source cross-platform multimedia development API/library designed to provide fast access to the graphics framebuffer and audio device. SDL is currently being applied to a number of Embedded Linux implementations such as Microwindows. details

Tiny-X — a small footprint X Window server implementation for embedded systems. It was developed by Keith Packard of the XFree86 Core Team, sponsored by SuSE. The goal was to create something that would work well in a small memory footprint and, importantly, be robust in near out-of-memory situations. Typical X servers based on Tiny-X can fit in less than 1MB on x86 CPUs. The project has since forked into several projects, including KDrive, SmallX, and Integrated Tiny-X.

ViewML — a freely available, open source web browser targeted specifically at the embedded Linux platform. Currently, ViewML along with it's interface requires 2.1 MB of RAM, with a disk image of only 760K. — details

WML Browser — a project, sponsored by 5NINE to develop a browser which will allow any wireless device to have WAP functionality. It must support multiple protocol stacks (WAP 1.2.1, http), in differing environments, using differing input devices. The browser will work with framebuffer graphics. — details

Xynth Windowing System — a free software project to build a portable, embedded client-server windowing system. The Xynth Windowing System, released under the GPL, offers a lightweight GUI-capable windowing system usable in Linux-based embedded systems and devices, such as handhelds and set-top boxes. details

“Commercial” Embedded Linux Graphics System Software

Access: Netfront browser — an embedded browser designed for information appliances with modest memory and CPU performance. It requires less than 1.3MB ROM and 2MB RAM, supports full HTML 3.2 and selected features from HTML 4.0, frames, JavaScript, cookies, Web-printing and multi-languages. Its modular and scalable architecture can be enhanced by application-specific modules and plug-ins. An independent user interface layer and design tool allows device manufacturers to create a unique look and feel for their product. — details

ANT: Freesco browser — a small memory footprint, standards-compliant JAVA based browser that enables OEMs to quickly and easily design a branded interface for Internet appliances. It is platform-independent, so it can be used with any hardware or operating system environment (including various implementations of Embedded Linux). — details

Century Software: PIXIL PDA and Microwindows — a complete PDA system including an operating environment, PIM applications, email client, web browser, and a set of multimedia applications. The Microwindows graphical windowing system (described above) is at the core of the PIXIL PDA solution. — details

Espial: Espial Suite — a complete, 100% Java application layer that sits independently from the operating system and JVM on the upper layer of a device stack and has been used extensively with Linux. Espial Suites include the following applications: Espial DeviceTop graphical OSGi client, Espial Escape web browser, Espial Ebox email client, and Espial Espresso lightweight GUI toolkit.

Swell Software: LinuxPEG — LinuxPEG is an embedded GUI library and development toolkit designed specifically for embedded systems. The LinuxPEG library is designed to run on any Linux distribution and its development tools run in the X11 development environment. LinuxPEG, which is available under license, is small footprint, completely ROMable, includes full C++ source code, and is royalty fee. — details

Trolltech: Qtopia and Qt/Embedded — Qtopia is a mobile device window environment and application suite for PDAs, palmtop computers, Internet appliances, and similar devices. Qtopia is based on Qt/Embedded (described above), and includes PIM applications, Internet clients, entertainment and games, utilities, and more. Qtopia/PDA is available in commercial or open source licenses, while Qtopia Phone Edition is commercial-only. — details